Recently, a lamp using a semiconductor light emitting element with little power consumption and long life has been used in place of a filament type lamp. Especially, an electric bulb with a ferrule, such as a LED lamp which uses light emitting diodes as the light source, is adopted for various lighting equipments. In constituting the lamp with the ferrule using the light emitting diodes as a light source, it is necessary to make the lamp not only small but low cost taking advantages of the light emitting diodes.
For example, Japanese Patent Application Laid Open No. 2003-59330 (Patent Application (1)) discloses a LED lighting equipment using a LED module in a shape of an approximately plate which is easily wired. A terminal base is provided in the module to directly connect a power supply wire to the LED module in which a plurality of LED diodes is arranged on the plate. Moreover, Japanese Patent Application Laid Open No. 2006-313718 (Patent Application (2)) discloses a LED lamp including a filament type bulb having frame components, a point-like light source, a ferrule, and a translucent cover.
However, in the Patent Application (1), the power supply wire for the LED diodes is connected to a connecting portion formed on a surface of a substrate by drawing the power supply wire outside from the back side of the substrate. Therefore, the power supply wire is projected from a perimeter edge of the substrate, which results in enlargement of outer diameter of a base body of the lamp inevitably in order to take electric insulation distance from the base body of the lamp when the LED module is provided in the base body of the lamp. Accordingly, it becomes difficult to make the lamp small.
Furthermore, in the Patent Application (2), two insulating covering electric wires coupled to a point-like light source are electrically connected a patterned layer of a light source substrate by soldering after passing along a hole formed in the substrate as shown in a paragraph [0032] and FIG. 4 especially. That is, in the Patent Application (2), the electric supply wire to the light emitting diode is inserted in the substrate without taking around on the outside of the substrate as shown in (1). However, generally, the substrate is formed of metal plates with a good thermal conductivity, such as aluminum to effectively dissipate the heat from the light emitting diodes which are arranged on the surface of the substrate through an insulating layer. Accordingly, a sharp edge is formed in a through-hole to insert the wire. The sharp edge may damage the covering of the wire. Since two thin covering electric wires are used in order to flow a direct current with a lower voltage of about 24V to the light emitting diode, the thin covering of the wire tends to suffer damage. For this reason, although there is a method of cutting off the corner of the hole, it is difficult to cut off the corner because the metal plate of the substrate consists of a thin plate. Although it has been carried out to protect the electric wire by inserting a protection tube in the hole, the arrangement results in a problem that the manufacturing cost is raised because of the increase in numbers of components and manufacturing steps. In general, a protection tube is fixed in a through-hole by providing a hooking piece at both ends of the protection tube. The hooking piece is engaged at the opening of the through-hole. In this case, the hooking piece is interposed between the substrate and a radiator (frame component). Accordingly, adhesiveness between the substrate and the radiator is weakened, and the radiation efficiency is lowered.